So just very recently my berry has started to randomly delete my call log and text inbox. I have a lot of pictures on the phone but that's about the only thing that has changed recently.
Your almost certainly low on memory. Check. Your memory as mentioned and if its below 10000000 then you need to take action. First do a battery pull thern get a memory card and move all your pics to it. Then spend a minute searching for instructions on managing your memory. There is plenty of info here to get you fixed up.
Tp
Posted from my CrackBerry at wapforums.crackberry.com
A media card won't help your device memory. Search the forum and you will find information on how to increase your free memory. At the very least, you should monitor it and do a battery pull occasionally to free up used memory.
CJB as MM says the media card is just one step actually. It will help if you move pics, tones etc to the card but low memory is often times user related issues. The card is for storage only. If you are never deleting texts, or BBM conversations, have 20 themes on your device, etc. You should remove the apps or themes you dont use or need and understand that this will happen again if you dont address the issue.